Studies will be conducted on the development of CNS regulation of sympathetic nerve activity in neonatal rats. Development of baro- and chemoreceptor reflexes will be tested by measuring sympathetic nerve during asphyxia, hypoxia and hypercapnia and during hypo- and hypertension induced by pharmacological agents. The relationship between development of physiological end organ response, synaptogenesis and ganglionic neurotransmission will be studied in the cervical sympathetic pathway. Development of pre- and postganglionic sympathetic activity will be studied in spontaneously hypertensive neonatal rats to see if there are abnormalities in the developmental process.